Occurrence: Worldwide. Species affected: All. Age affected: All. Deficiency takes 3 weeks to develop.

Causes: Deficiency of vitamin B1 (thiamine) in the diet or Amprol excess can be caused by mouldy feed or oxidation by rancid fat.

Effects: Nervousness, anorexia, ruffled feathers, leg weakness and an unsteady gait can be seen. Paralysis and star gazing can occur in young birds. Adults may have a blue comb, decreased respiration rate and low...